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Terminology
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The term “plate” refers to the subdivision of the earth’s
crust and lithosphere.
The term “tectonics” refers to the deformation of the earth’s
crust.
“Plate tectonics” refers to the formation and migration of
these plates.
Subduction zone is where two plates come together, and
one is forced below the other.
It is puzzling!
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Alfred Wegener developed a
theory that states that all
present continents were once
together and collectively
known as a 'supercontinent'
called a Pangaea.
The Pangaea theory was
treated with much skepticism
when it was first raised. But
since then, there have been
much evidence to support this
theory.
There are 3 types of boundaries:
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Divergent plate boundaries
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Convergent plate boundaries
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Transform plate boundaries
Divergent plate boundaries
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Divergent plate boundaries are where two plates move apart or
separate
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Magma is heated by convection, rises and pushes the plates apart
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This creates a new sea floor
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Also called seafloor spreading
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Great Rift Valley in
Africa
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Mid-Atlantic Ridge
Back to boundary types
Convergent Boundaries
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This is where two plates come together
One plate is forced to sink below the other
Subduction zone
There are three types of convergent boundaries:
• Ocean-continent
• Ocean-ocean
• Continent-continent
Back to types of boundaries
Oceanic-continental
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The subduction zone is where the oceanic plate is forced below
the continental plate.
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A deep trench is formed off shore
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A mountain range is formed on land
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An example is the West coast of North America
Back to convergent boundaries
Oceanic-Oceanic
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Where two oceanic plates
converge
A deep ocean trench is
formed
A island chain of volcanoes is
formed
Examples would be Hawaii or
Japan
Back to convergent boundaries
Continent-Continent
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Where two continental plates come together
The plates push together to form a chain of high, jagged
mountains
Examples would be The Himalayas
back
Transformation boundaries
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This occurs between two
plates that scrape against
each other
At this type of boundary, a
fault is created
A common result is an
earthquake
A very well known example is
the San Andreas Fault in
California
Now, let’s review!
1) At a divergent plate boundary, how
do plates move?
a) Grind past each other
b) Collide with each other
c) Rift apart
d) Move under each other
2) Oceanic trenches are formed by:
a) Sea-floor spreading
b) The collision of continents
c) The subduction of oceanic crusts into
the earth’s mantle
d) The subduction of continental crust
into the earth’s mantle
3) The supercontinent composed of
all of the continents proposed by
Alfred Wegener is called:
a) Mantle
b) Pacific
c) Pangaea
d) Plate tectonics
4) Where would an earthquake
happen?
a) At a divergent plate boundary
b) At a convergent plate boundary
c) At a transform plate boundary
5) What is not a result of plate
tectonics?
a) Hurricanes
b) Volcanoes
c) Earthquakes
d) Mountains